Fluid pressure actuated switch



y 1, 1963 P. s. SCHOLZ 3,090,848

FLUID PRESSURE ACTUATED SWITCH Filed Nov. 6, 1959 ATTORNEY Patented May 21, 1963 3,tl%,848 FLUID PRESSURE ACTUATED SWKTCH Peter S. Schulz, Cranford, NJ., assignor to Paragon Products Corporation, Newark, NJ a corporation oi New Jersey Filed Nov. 6, 1959, Ser. No. 851,324 1 Claim. (Cl. filth-d3) This invention relates to fluid pressure operated electric switches, and more particularly to a novel and simple switch of this type arranged to control an electric circuit responsive to variations in fluid pressure.

Switches of this type are used to open or close electrical circuits in order to indicate pressure conditions within a fluid system, such as hydraulic or lubrication systems, for example. One particular use is in the automotive vehicle art, wherein these switches may be used to open or close an electric energizing circuit for an indicator light on the dashboard, responsive to a predetermined selected pressure or pressures in a hydraulic system. For example, a switch of this type may be used in the engine lubrication system to open the circuit of a dash or panel mounted indicator lamp when the oil pressure in the lubricating system attains or exceeds a pre-set value. When the pressure drops below a pre-set value, the switch will reclose the energizing circuit for the indicator lamp and thus provide a warning to the driver of inadequately low pressure in the engine lubrication system.

Known switches of this type have generally included a flexible diaphragm as the member movable, responsive to pressure of the fluid, to open and close the switch contacts. Considerable difficulty has been experienced in maintaining fluid-tight sealing of such diaphragms, and the diaphragms frequently rupture and leak during operation of the switch. One of the reasons for such rupturing has been the fact that the diaphragm carried the movable contact of the switch, which contact has been substantially smaller in area than the diaphragm. The flexing of the diaphragm resulted in a bending stress concentration at the periphery of the contact which condition, in turn, promoted rupturing in this area of the diaphragm.

Another important factor is that such diaphragms were subjected to the full pressure of the fluid over a large nonreinforced area of the diaphragm, and furthermore have had to withstand the full force of the biasing means acting against the pressure of the fluid. This factor also contributed to rapid failure of the diaphragm in service.

While various expedients have been proposed to mitigate or correct these conditions, the proposed solutions have been either unsuccessful in operation or economically unfeasible from the standpoint of commercial practicability.

In accordance with the present invention, it has been found that a reliable fluid pressure operated switch can be provided by superposing an imperforate flexible diaphragm of dielectric material carrying the movable contact on a relatively rigid metal partition member forming the fixed contact, the diaphragm and partition memher being peripherally supported and clamped between a pair of housing members conjointly defining a chamber divided into two non-communicating sections by the diaphragm. The partition member is on the fluid pressure application side of the diaphragm, and has a flat annular rim sealingly clamped between the periphery of the diaphragm and a sealing washer or gasket.

The metal partition member has a central, substantially frusto-conical, relatively shallow dished section with a substantially flat base. This base has a plurality of aperturcs therein and a diameter of the order of that of a dished metal spring seat centered on the side of the diaphragm remote from the partition and anchored to the diaphragm by a headed metal rivet forming the movable switch contact.

The diaphragm is normally biased into substantially conforming relation with the partition, with the rivet in contact with the latter, by a coil spring engaging the spring seat and also engaging a metal washer at the outer end of a dielectric housing member and secured in place by the non grounded terminal of the switch. The other housing member is metal and is in contact with the metal diaphragm to act as a grounding terminal for the switch.

The metal partition, and its shallow dished recess or central offset, support the diaphragm to relieve it of any excessive stress due to the biasing coil spring. As the diaphragm merges smoothly into the frusto-conical recess in the partition, there are no diaphragm areas or zones subjected to excessive bending stresses, thus prolonging the diaphragm life.

The fluid under pressure can act on the diaphragm only through the apertures in the base of the offset, and thus only against that area of the diaphragm reinforced by the flat dished spring seat. Furthermore, the dielectric housing member is formed with means engageable with the spring seat to limit movement of the diaphragm away from the partition offset to an amount sufficient to separate the contacts to open the switch but insufficient to lift the radially outer portion of the diaphragm out or" substantial engagement with the partition. In the open position of the contacts, the diaphragm is substantially flat, thus further reducing the bending or flexing stresses thereon.

For an understanding of the invention principles, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawings. In the drawings:

FIG. 1 is an elevation view of a normally closed fluid pressure actuated switch embodying the invention;

H6. 2 is an exploded axial sectional view illustrating the parts of the switch;

FIG. 3 is an axial sectional view through the assembled switch in the circuit closing position;

FIG. 4 is a partial axial sectional view through the as sembled switch illustrating the parts in the circuit opening position; and

FIG. 5 is a plan view of the metal partition member.

The pressure fluid operated switch of the present invention is applicable to any pressure fluid or oil circulating system wherein it is desired to have an electric circuit controlled responsive to the pressure within the system. However, and solely by way of example, the invention is illustrated as embodied in a switch particularly designed to be connected to a lubricating system for the engine of an automotive vehicle, so as to close a circuit including a panel mounted warning lamp whenever the pressure in the lubricating system is below a pre-set value. When such pressure equals or exceeds such pre-set value, the lamp circuit is opened so that the warning lamp is extinguished.

The switch 1th illustrated in the drawings comprises a conductive metal housing member 20 and a second housing member of dielectric material 30. Housing member 20 may be formed of any suitable electrically conductive metal such as carbon or alloy steel, brass, copper or the like. Housing member 30 may be formed of any suitable dielectric or nonelectrically conductive material, such as Bakelite, nylon, and the like.

The metal housing member 29 includes a tubular stem portion 21 formed with external threads 22 and an axial passage 23. Stem 21 is integral with a generally cylindrical and relatively enlarged head 25 having a cylindrical flange 26 bounding a flat annular seat 27 surrounding a frusto-conical recess 28 in communication a,oso,sas

with bore 23. The exterior periphery of flange 26 is formed with flats 29A alternating with recesses 29B, for receiving suitable wrench means for threading stem 21 into a female fitting of the lubrication system.

The dielectric housing member 30 is generally frustoconical in form with an enlarged substantially cylindrical base 31, providing a flat annular seating surface 32, facing seat 27, and having a shoulder 33. Housing member 30 has a passage or recess 34 extending axially from the larger end thereof and coaxial with a smaller diameter passage 36 through its outer end wall 37. The larger end or base of member 3% has an annular recess 35 therein bounded by the enlarged head 31 and by a circular lip 32 terminating slightly short of the plane of seating surface 32.

An electrically conductive terminal member 15 has a stem 11 extending through passage or aperture 36 and a shoulder 12 seating against end wall 37. The inner end of stem 11 is riveted or spun over against an electrically conductive metal washer 13 to secure the terminal 15 and washer 13 to the dielectric member 39. Washer 13 has a diameter nearly equal to the diameter of passage or cylindrical recess 34.

An important feature of the invention is the provision of the apertured metal partition member 40 serving as a support for the imperforate flexible diaphragm and regulating the application of fluid pressure to the latter. Metal partition member 40 has a flat rim portion 42 seated against a sealing gasket or washer 41, preferably of dielectric and resilient cushioning material, seated against seat 27. The diameter of member 4 3 is such that its periphery is in physical and electrical contact with the cylindrical rim 26 of member 20. The central portion of partition 4% has a relatively shallow, frusto-conical, dished offset portion 43 centrally thereof, and the flat part base 44 of dished portion 43 is formed with a series of apertures 45.

A circular diaphragm 50 of dielectric and flexible material is seated against metal partition 40 and has a diameter substantially equal to the diameter of member 49. Diaphragm St) is centrally apertured to receive a headed rivet of electrically conductive metal which secures a dished electrically conductive metal spring seat 55 in sealing relation to the surface of diaphragm t opposite to that facing partition 40. Spring seat 55 has a flat base 56 lying against diaphragm 50', and base 56 has a diameter of the order of that of the flat portion 44 of partition 49. A coil spring 66, of electrically conductive metal, is disposed in passage 34 and has its outer end seated against washer 13 and its inner end engaging seat 55. Coil spring 66 thus establishes electrical contact between terminal 15 and contact rivet 51.

In assembling the switch, washer 41 is placed against seat 27 and then metal partition at is sealed on washer 41. The flexible diaphragm 50 is then seated on the metal partition 40 and coil spring 60 is placed into passage 34. After this, dielectric housing member 30 is telescoped into the cylindrical rim 26 so as to firmly hold the peripheral margins of partition 40 and diaphragm St} between seats 27 and 32. The upper thinner edge of cylindrical rim 26 is then spun over the shoulder 33 of member 30, as indicated at 24, to firmly anchor the several parts in proper assembled relation. When the parts are so assembled, spring 60 forces seat 55 toward partition 40 until contact 51 engages the partition. Diaphragm 59 is thereby in substantially conformingly supported engagement with partition 46.

To use the switch 10, the stem 21 is threaded into a suitable female fitting in the engine lubricating system (or in any other pressure fluid system whose pressure is to be indicated). One conductor of the circuit to be controlled is then connected to terminal 15, and the other conductor connected through an indicating lamp or the like to a source of potential preferably having a grounded terminal. A circuit is thus completed to ground between terminal 15 and the housing member 20. The pressure fluid will flow through the apertures 45 and thus act against the surface of flexible diaphragm 50, backed by seat 55. When the pressure exceeds a pre-set value, determined by the strength of spring 64 the diaphragm 50 will be forced away from the partition 40 sufliciently to break the electrical contact between rivet 51 and partition 40. This will open the control circuit to extinguish the warning or indicator lamp. Conversely, should the pressure fall below a predetermined value, the force of spring 60 will overbalance the pressure of the fluid in chamber or recess 23 and will move diaphragm 50 toward partition 4 to re-engage contact rivet 51 with partition 40 and thus reclose the indicating or warning lamp circuit.

When diaphragm 50 is forced away from partition 40 by the pressure of the fluid acting through apertures 45, seat 55 engages lip 38 when diaphragm 50 is substantially flat and uniplanar. In this position, the annular area of diaphragm 50 corresponding to rim 42 seats flush against this rim so that diaphragm 50 is not flexed or stressed around the periphery of seat 55. Conversely, when switch re-closes, diaphragm 5d moves into smoothly conforming supported relation with partition 40 without any sharp flexing about the periphery of seat 55 or about the periphery of the shallow recess 44 in partition 4t). Thereby, the life of diaphragm 50 is greatly prolonged.

In both the opening and closing of the switch, the relatively small apertures 45 restrict flow of fluid between recess 28 and dished portion 44. This stabilizes switch 10 against operating on momentary pressure fluctuations.

While a specific embodiment of the invention has been described in detail to illustrate the application of the invention principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

A fluid pressure operated switch comprising, in combination, means defining a housing including a fluid chamber of electrically conductive metal and an unrestricted bore leading into said chamber and arranged for connection to a source of fluid under pressure; a fixed electrically conductive metal partition extending across said chamber in electrical contact therewith and having a central portion formed With a plurality of relatively small diameter apertures for restricted flow of fiuid therethrough, said partition constituting a first contact of said switch; a flexible imperforate diaphragm assembly superposed on said partition on the surface thereof away from said bore, and including a flexible diaphragm of dielectric material, having its periphery in fluid-tight engagement with said housing and in direct fluid-tight engagement with the periphery of said partition, to form a fluid-tight seal for said chamber, a second switch contact carried centrally by said diaphragm, and a shallow dished metal spring seat secured to the surface of said diaphragm away from said partition by said second contact, and having a base area of the order of that of said apertured central portion of said partition; a coil spring in said housing engaged with said spring seat and normally biasing said diaphragm smoothly against said partition to engage said first and second contacts; said partition limiting deflection of said diaphragm by said coil spring substantially to a position in which said first and second contacts are engaged; the central portion of said diaphragm, when the pressure of the fluid in said chamber acting through said flow restricting apertures against the diaphragm exceeds the force of said coil spring, moving away from said partition to disengage said contacts; and means engageable with said spring seat and limiting outward movement of the central portion of said diaphragm; said apertures restricting flow of fluid between said bore and said diaphragm to protect said diaphragm against the effect of sudden pressure increases in said fluid chamber.

(References on following page) References Citeqi in the file of this patent UNITED STATES PATENTS Heymann et a1. Oct. 12, 1948 6 Shaw Ian. 4, 1955 Brown et a1. Feb. 26, 1957 Byam Aug. 4, 1959 FOREIGN PATENTS Germany May 14, 1958 

